Usage And Storage, avoid excessive heat, store compostable bags in a cool, dry place, and used them within one year of purchase. The highest bio-based content, Unni Compostable Bags are made from the starches of plants and contains NO polyethylene. These bags are durable and reliable, while being good for the environment. Certified in U.S. and EUROPE, denotes certification by the Biodegradable Products Institute (BPI) with the U.S. standard ASTM D6400. Also certified by European OK Compost Home as compostable in backyard or home composting facilities, this is one of the worlds only home composting certifications, and it is based on the European standard EN 13432.